System for a Utility Vehicle Comprising a Screw Compressor and an Electric Motor With a Common Cooling System

ABSTRACT

A system for a utility vehicle has a compressor, an electric motor and an electronic drive system. The electric motor drives the compressor. The electric motor, the compressor and the electronic drive system have a common cooling circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No. PCT/EP2017/073553, filed September 19, 2017, which claims priority under 35 U.S.C. § 119 from German Patent Application No. 10 2016 011 503.3, filed Sep. 21, 2019, the entire disclosures of which are herein expressly incorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a system for a utility vehicle comprising a screw compressor and an electric motor.

Screw compressors for utility vehicles are already known in the prior art. Such screw compressors are used in order to provide the needed compressed air for the brake system of the utility vehicle, for example.

In this context, especially oil-filled compressors are known, especially also screw compressors, the purpose of which is to regulate the oil temperature. This is generally accomplished in that an external oil cooler is present, which is connected to the oil-filled compressor and the oil circuit across a thermostatic valve. The oil cooler here is a heat exchanger having two circuits separated from each other, the first circuit being provided for the hot fluid, i.e., the compressor oil, and the second one for the cooling fluid. The cooling fluid used may be for example air, water mixtures with an antifreeze, or another oil.

This oil cooler must then be connected to the compressor oil circuit via pipes or hoses and the oil circuit must be protected against leakages.

This external volume must furthermore be filled with oil, so that the overall quantity of oil is increased. In this way, the inertia of the system is increased. Furthermore, the oil cooler must be mechanically accommodated and secured, either by existing supports located around it or by a separate support, which requires additional fastening means, as well as design space.

A screw compressor with integrated oil cooling is already known from U.S. Pat. No. 4,780,061.

Furthermore, DE 37 17 493 A1 discloses a screw compressor layout arranged in a compact housing, having an oil cooler on the electric motor of the screw compressor.

A compressor flange for a screw compressor is known from DE 10 2010 015 151 A1.

Moreover, a connection flange for a heat exchanger of a motor vehicle having cooling ducts is known from US 2014/0190674 A1.

Moreover, a heat exchanger with a flange connection is known from DE 10 2013 011 061 B3, wherein the flange connection has an attachment flange which is a die cast part and has passages that are made by casting technology to receive screw bolts.

An arrangement of an electronic cooler and an electric motor is already known from US 2003/143090 A1.

Moreover, a cooling layout is known from US 2012/076679 A1 in which an electric motor and the electronic drive system likewise have a cooling layout.

The problem which the present invention proposes to solve is to modify a system for a utility vehicle comprising a screw compressor and an electric motor in an advantageous manner, especially such that a space-saving cooling possibility can be provided for a system of this kind.

This problem is solved according to the invention by a system for a utility vehicle comprising a screw compressor as well as an electric motor with the claimed features. It is provided that a system for a utility vehicle comprises a compressor, an electric motor and an electronic drive system, wherein the electric motor drives the compressor. The electric motor, compressor and electronic drive system have a common cooling circuit.

The invention is based on all components of the system for a utility vehicle comprising the compressor, electric motor and electronic drive system being cooled with the same cooling fluid. In this way, an especially efficient cooling management is provided for a corresponding compressor system.

Preferably, the cooling elements are connected in series, so that all of them have the same flow rate of coolant.

The compressor may be, in particular, a screw compressor. Such screw compressors are especially suitable in novel applications for hybrid utility vehicles in which a compressor for generating compressed air is not constantly driven by the drive unit of the utility vehicle.

Furthermore, it may be provided that the cooling circuit has a coolant duct which is formed for at least a portion by a succession of cooling elements. This series connection enables a simple construction. Furthermore, the pressure variation in the coolant circuit can be more easily adjusted overall.

In particular, it may be provided that at least one cooling element is coordinated respectively with the electric motor, the compressor and the electronic drive system. Such cooling elements may be heat exchanger elements, for example, which can be hooked up in series in the cooling circuit, for example. The provision of corresponding cooling elements for the individual system components makes possible a needs-based heat dissipation.

Furthermore, it may be provided that the electric motor has a starter cooling element, wherein the cooling elements are arranged such that coolant in the cooling circuit flows at first through the cooling element of the electronic drive system, then through the starter cooling element and then through the cooling element of the compressor. This affords the advantage that the cooling element must first dissipate the majority of the heat, namely the cooling element of the electronic drive system is the first to be flowed through. This makes it possible to easily manage temperature increases in the electronic drive system and to easily establish temperature regulation here in the range of acceptable operating temperatures. Furthermore, this arrangement takes account of the fact that the most important range of the temperature regulation occurs in the area of the electronic drive system, since overheating must be avoided here in all cases. Furthermore, the electronic drive system has a high thermal radiation on account of high energy losses in the electronic drive system, for which reason an adequate heat dissipation is required. Moreover, it must be ensured that little pressure loss occurs in the cooling circuit in order to keep the pump energy needed to pump the coolant through the cooling circuit low.

Moreover, however, it may be provided that the electric motor also comprises a housing cooling element, wherein the cooling elements are arranged such that coolant in the cooling circuit flows at first through the housing cooling element upstream from the cooling element of the electronic drive system. This kind of cooling is relatively noncritical, since little heat uptake in the housing cooling element is to be expected here. The pressure drop is also relatively slight.

Furthermore, it may be provided that the cooling element of the electronic drive system comprises a flow divider. Owing to the flow divider it becomes possible to avoid pressure losses in the cooling element of the electronic drive system, since in this way the flow cross sections of the cooling duct can be adjusted accordingly. In particular, in this way a high cooling efficiency and heat dissipating ability is provided while at the same time preventing too large a pressure drop in the cooling element.

Furthermore, it may be provided that the cooling element of the electronic drive system comprises a substantially W-shaped flow duct. In this way, it is ensured that the coolant flows in a meandering manner through the cooling element of the electronic drive system and thereby flows across a large surface of the electronic drive system, so that on the whole good heat dissipation is made possible in the area of the electronic drive system.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional representation of an exemplary embodiment according to the invention for a system for a utility vehicle comprising a screw compressor and an electric motor.

FIG. 2 is a schematic diagram of the cooling layout of the system for a utility vehicle.

FIG. 3 is a perspective view of the structure of the cooling layout of FIG. 2.

FIG. 4 is a schematic view of the structure of the cooling element for the electronic drive system

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in a schematic cross sectional representation a screw compressor 10 in the sense of an exemplary embodiment of the present invention.

The screw compressor 10 has a fastening flange 12 for the mechanical fastening of the screw compressor 10 to an electric motor (not otherwise shown).

However, the input shaft 14 is shown, by means of which the torque from the electric motor is transmitted to one of the two screws 16 and 18, namely the screw 16.

The screw 18 meshes with the screw 16 and is driven by it.

The screw compressor 10 has a housing 20, in which the basic components of the screw compressor 10 are accommodated.

The housing 20 is filled with oil 22.

At the air inlet side, an inlet port 24 is provided on the housing 20 of the screw compressor 10. The inlet port 24 is designed such that an air filter 26 is arranged in or on it. Furthermore, an air inlet 28 is provided radially at the air inlet port 24.

In the region between inlet port 24 and the place where the inlet port 24 is mounted on the housing 20, there is provided a spring-loaded valve insert 30, designed here as an axial seal.

This valve insert 30 serves as a check valve.

Downstream from the valve insert 30, there is provided an air supply duct 32, which supplies the air to the two screws 16, 18.

At the exit side of the two screws 16, 18, there is provided an air outlet pipe 34 with a riser line 36.

In the region of the end of the riser line 36, there is provided a temperature sensor 38, by which the oil temperature can be monitored.

Furthermore, a holder 40 for an air deoiling element 42 is provided in the air outlet region.

The holder 40 for the air deoiling element comprises the air deoiling element 42 in the mounted condition in the region facing toward the bottom (as also shown in FIG. 1).

Furthermore, there is provided inside the air deoiling element 42, a corresponding filter screen or known filter and oil separator devices 44, not otherwise specified in detail.

In the upper central region, in terms of the mounted and operational conditions (that is to say as shown in FIG. 1), the holder 40 for the air deoiling element 42 has an air exit opening 46 leading to a check valve 48 and a minimum pressure valve 50. The check valve 48 and the minimum pressure valve 50 may also be formed in a common combined valve.

After the check valve 48 there is provided the air outlet 51.

The air outlet 51 is generally connected to accordingly known compressed air consumers.

In order to again return the oil 22 separated and located in the air deoiling element 42 to the housing 20, there is provided a riser line 52, having a filter and check valve 54 at the exit of the holder 40 for the air deoiling element 42 at the passageway into the housing 20.

Downstream from the filter and check valve 54, a nozzle 56 is provided in a housing bore. The oil return line 58 leads back to roughly the central region of the screw 16 or the screw 18 in order to supply oil 22 to them once more.

In the bottom region of the housing 20 in the mounted state there is provided an oil drain plug 59. Through the oil drain plug 59, a corresponding oil drain opening can be opened up, by means of which the oil 22 can be drained.

In the lower region of the housing 20, the shoulder 60 is also present, on which the oil filter 62 is secured. Via an oil filter inlet duct 64, which is situated in the housing 20, the oil 22 is taken at first to a thermostatic valve 66.

In place of the thermostatic valve 66 there may be provided an open-loop and/or closed-loop control device, by which the oil temperature of the oil 22 present in the housing 20 can be monitored and set at a target value.

Downstream from the thermostatic valve 66 is the oil inlet of the oil filter 62, which takes the oil 22 back across a central return line 68 to the screw 18 or to the screw 16, but also to the oil-lubricated bearing 70 of the shaft 14. In the region of the bearing 70, a nozzle 72 is also provided, being provided in the housing 20 in connection with the return line 68.

The cooler 74 is connected to the shoulder 60.

In the upper region of the housing 20 (relative to the mounted condition), there is a safety valve 76, by which excessive pressure in the housing 20 can be released.

Upstream from the minimum pressure valve 50 is a bypass line 78 leading to a relief valve 80. Through this relief valve 80, which can be actuated by way of a connection to the air supply 32, air can be returned to the region of the air inlet 28. In this region there may be provided a vent valve, not otherwise shown, and also a nozzle (constricting the diameter of the supply line).

Furthermore, an oil level sensor 82 may be provided at approximately the height of the line 34 in the outer wall of the housing 20. This oil level sensor 82 may be an optical sensor, for example, and of such a nature and layout that it is possible to recognize from the sensor signal whether the oil level during operation is above the oil level sensor 82 or whether the oil level sensor 82 is exposed and accordingly the oil level has dropped.

In connection with this monitoring, an alarm unit may also be provided, which puts out or relays a corresponding error message or warning message to the user of the system.

The function of the screw compressor 10 shown in FIG. 1 is as follows.

Air is supplied via the air inlet 28 and flows across the check valve 30 to the screws 16, 18, where the air is compressed. The compressed air and oil mixture, which rises via the riser pipe 36 through the outlet line 34 with a compression factor of 5 to 16 times after the screws 16 and 18, is blown directly onto the temperature sensor 38.

The air, which still carries some oil particles, is then taken across the holder 40 into the air deoiling element 42 and, once the corresponding minimum pressure is attained, into the air outlet line 51.

The oil 22 located in the housing 20 is held at the operating temperature via the oil filter 62 and possibly via the heat exchanger 74.

As long as no cooling is needed, the heat exchanger 74 will not be used, nor even turned on.

The corresponding turning on takes place via the thermostatic valve 68. After being cleaned in the oil filter 64, oil is supplied via the line 68 to the screw 18 or the screw 16, and also to the bearing 72. The screw 16 or the screw 18 is supplied via the return line 52, 58 with oil 22, and the cleaning of the oil 22 occurs here in the air deoiling element 42.

The screws 16 and 18 of the screw compressor 10 are driven by the electric motor (not otherwise shown), which transfers its torque through the shaft 14 to the screw 16, in turn meshing with the shaft 14.

The relief valve 80, not otherwise shown, ensures that the high pressure prevailing in the operating state at the outlet side of the screws 16, 18 is not contained in the region of the supply line 32, but rather a low inlet pressure, especially atmospheric pressure, constantly exists in the area of the supply line 32, especially when starting the compressor. Otherwise, a very high pressure at the exit side of the screws 16 and 18 would occur at first when starting the compressor, excessively stressing the drive motor.

FIG. 2 shows in a schematic arrangement the cooling layout for an exemplary embodiment of a system 1 according to the invention for a utility vehicle comprising a compressor 10, as shown in FIG. 1, i.e., a screw compressor 10.

However, there can be provision in principle that any given type of compressor may be used in the system 1.

The system 1 furthermore has an electric motor 5 and an electronic drive system 6. The cooling circuit 100 here serves for removing heat from the electric motor 5, compressor 10 and electronic drive system 6.

The electric motor 5, the compressor 10 and the electronic drive system 6 thus have a common cooling circuit 100.

The overall cooling system 100 comprises several cooling elements, namely a cooling element for the electronic drive system 102, a stator cooling element 103 of the electric motor, and a compressor cooling element 104.

First of all, a housing cooling element 101 is connected to the coolant inlet 105, which element 105, however, leads directly to the cooling element of the electronic drive system 102.

However, there can also be provision that the coolant inlet 105 is connected directly to the cooling element of the electronic drive system 102. From the cooling element of the electronic drive system 102, the liquid coolant 106 flows to the stator cooling element 103 for the electric motor 5 and then to the cooling element 104 of the compressor 10. After this, the coolant is taken to an internal or external cooling duct or cooling hose 107. From the cooling element 104, the coolant then flows through the coolant outlet 108 into the rest of the cooling circuit, where it can be driven for example by a pump.

FIG. 4 shows in perspective view the layout of the system 1 as shown schematically in FIG. 3.

Since the cooling element 102 of the electronic drive system 6 needs to carry away most of the heat in order to avoid excessively high temperature increases in the region of the electronic drive system 6, a special configuration is provided here.

The cooling element 102 of the electronic drive system 6 has a substantially W-shaped flow duct 102 a.

Furthermore, a flow divider 102 b is provided in the cooling element 102 of the electronic drive system 6.

The coolant duct here has a sufficient cross section to have a low pressure drop between cooling element inlet 109 and cooling element outlet 110. Owing to the flow divider 102 b, the flow velocity in the interior of the cooling duct continues to be kept high, since an excessive dropping of the flow velocity here is prevented by the flow divider 102 b.

LIST OF REFERENCE SYMBOLS

-   1 System -   5 Electric motor -   6 Electronic drive system -   10 Screw compressor -   12 Fastening flange -   14 Input shaft -   16 Screws -   18 Screws -   20 Housing -   22 Oil -   24 Inlet port -   26 Air filter -   28 Air inlet -   30 Valve insert -   32 Air supply duct -   34 Air outlet pipe -   36 Riser line -   38 Temperature sensor -   40 Air/oil separator -   42 Oil trap -   44 Filter screen or known filter and oil separator devices -   46 Air exit opening -   48 Control valve -   50 Minimum pressure valve -   51 Air outlet -   52 Riser line -   54 Filter and control valve -   56 Choke -   58 Oil return line -   59 Oil drain plug -   60 Shoulder -   62 Oil filter -   64 Oil filter inlet duct -   66 Thermostatic valve -   68 Return line -   70 Bearing -   72 Choke -   76 Safety valve -   78 Bypass line -   80 Relief valve -   82 Oil level sensor -   100 Cooling circuit -   101 Housing cooling element -   102 Cooling element for electronic drive system -   102 a Flow duct -   102 b Flow divider -   103 Stator cooling element -   104 Compressor cooling element -   105 Coolant inlet -   106 Coolant -   107 Cooling duct/cooling hose -   108 Coolant outlet -   109 Cooling element inlet -   110 Cooling element outlet

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

What is claimed is:
 1. A system for a utility vehicle, comprising: a compressor; an electric motor; and an electronic drive system, wherein the electric motor drives the compressor, and the electric motor, the compressor and the electronic drive system have a common cooling circuit.
 2. The system as claimed in claim 1, wherein the compressor is a screw compressor.
 3. The system as claimed in claim 1, wherein the common cooling circuit has a coolant duct which is formed for at least a portion by a succession of cooling elements.
 4. The system as claimed in claim 3, wherein at least one cooling element is coordinated, respectively, with the electric motor, the compressor and the electronic drive system.
 5. The system as claimed in claim 4, wherein the electric motor has a stator cooling element, wherein the cooling elements are arranged such that coolant in the common cooling circuit flows at first through a cooling element of the electronic drive system, then through the stator cooling element, and then through a cooling element of the compressor.
 6. The system as claimed in claim 5, wherein the electric motor further comprises a housing cooling element, wherein the cooling elements are arranged such that coolant in the cooling circuit flows at first through the housing cooling element upstream from the cooling element of the electronic drive system.
 7. The system as claimed in claim 4, wherein the cooling element of the electronic drive system comprises a flow divider.
 8. The system as claimed in claim 7, wherein the cooling element of the electronic drive system comprises a substantially W-shaped flow duct. 